The field of invention is communication cables and specifically optical cable or fiber optic assemblies.
Communication cables, i.e. cables which carry a plurality of fiber optic cables or the like, are in wide use in today""s telecommunications industry. Communication cables are relatively long, frequently several hundred feet or longer. One end of the communication cable will be connected to a junction or cable box in which the fiber optic cables will be individually connected as required.
Installation of a communication cable to a cable box requires that a rigid, water-tight connection be made. In one prior art example illustrated by FIG. 1, the end of the communication cable for connecting to the cable box includes a coupling ring 1 having a male threaded outer surface which surrounds a center tunnel through which the communication cable 2 is run. A cable coupler 3 is tightened onto coupling ring 1 so that coupling ring frictionally engages the surface of communication cable 2. The other side of the coupling ring is then threadably connected to the cable box and nut 4 is used to secure in position.
In situations where ring 1 is first connected to the communication cable, it is necessary to rotate a portion of the communication cable as well.
This can cause a difficult installation in many situations. For example, an installing technician may not have sufficient length of free cable to easily rotate the cable (as tight working space and large bundles generally prevent this). To help alleviate this situation, today""s available connectors generally require five to nine various components, requiring multiple tightenings and orientations during assembly which add to the complexity of the installation as well as the required time to install.
A second example is presented in U.S. Pat. No. 5,425,121 issued to Cooke et al. In Cooke et al, an entry nut is threaded to an optical entry port and then a main body and back nut is threaded to secure attachment. Finally heat shrinkable tubing is positioned and heated to provide a water-tight seal.
Besides the extra effort on the part of the installing technicians, the result is that the communication cable can be undesirably twisted and the force retained in the twisted cable may eventually loosen the connection at the cable box. Such loosening could permit moisture to enter and damage the fiber optic cable resulting potentially in a significant loss of performance.
The purpose of my invention was to develop a cable connector which would provide a water-tight seal and be capable of installation by simple hand tightening without the need for tools of any kind.
My invention incorporates the use of: 1) an elongated tubular coupling nut permanently affixed to one end of a communication cable; and, 2) an elongated tubular coupling ring, which, on one side is designed to be threadably connected to the coupling nut and on the other side is designed to be threadably connected to a cable box. The coupling ring and nut combination can be designed to accommodate communication cables of various sizes which carry a plurality of fiber optic cable or the like.
Operatively coupling a communication cable to a cable box requires that a water-tight connection be made in order for the fiber optics contained therein to function properly in various weather conditions. As described above, my invention consists of only two components, namely a coupling ring and a coupling nut of which, only the coupling ring is adjusted during the installation process. Use of only two components significantly increases the ease and efficiency of an installation, thereby reducing the overall installation cost.
The coupling nut is sized to receive or accept the outer dimension of the communication cable. The coupling nut therefore receives the communication cable partially therein by inserting the end portion of the communication cable into one end of my coupling nut. The adjacent portion of cable within the coupling nut is thereafter secured in place using a sealant, preferably an epoxy. A sufficient lead for each fiber optic cable extends from the communication cable through the coupling nut and eventually through the coupling ring and into the cable box. This length is necessary so that technicians can eventually feed the fiber optic cables into the cable box and have sufficient lead length to make all necessary connections.
To facilitate a fast on-site installation of the communication cable to the cable box, the coupling nut should be installed off-site. Therefore, when brought to the installation site, the coupling nut will be secured to the communication cable with the fiber optic leads extending from the coupling nut.
Once the communication cable is permanently secured to the coupling nut by allowing the sealant an opportunity to cure, the cable leads are then passed thru the coupling ring which is an elongated tubular member having threaded end connections on either side. These threaded end connections have opposite thread orientations.
In the preferred embodiment, the coupling ring has a set of female threads for engaging the male threads on the coupling nut. The cable leads are next fed into the existing cable box through a threaded aperture, which is typically female threaded. Each lead is now in position to be operatively connected within the cable box and the communication cable is ready to be physically connected using my coupling nut and coupling ring.
The coupling nut is inserted into the coupling ring and positioned for threadable engagement. The mating threads of both the coupling nut and coupling ring have a reverse thread interface relative to the set of mating threads of the coupling nut and cable box. This reverse thread interface is designed to require essentially the same number of turns to tighten as is the case for the coupling ring/cable box interface, preferably 7.5 turns for complete threaded engagement.
The coupling nut is designed with a first O-ring positioned at the base of the reverse male threads for providing a first water seal between the mating surfaces of the coupling ring and coupling nut.
The first O-ring is intended to form a water-tight seal by complete threaded engagement of the coupling ring to the coupling nut. However, in situations where the coupling ring is overtightened, the O-ring could be damaged; allowing the potential for moisture to migrate and damage the fiber optics. Further, if not sufficiently tightened, the O-ring may not form a proper seal.
To insure that moisture is prevented from reaching the fiber optic cables, I have designed a second O-ring for positioning about the coupling nut. The second O-ring is unique because it is not dependent upon threaded engagement; it is appropriately sized so that it extends across the annulus between coupling nut and coupling ring.
The second O-ring is seated within a machined seat made about the circumference of the coupling nut and preferably positioned on the opposite side of the reverse threads from the first O-ring.
Most preferably, a second machined seat substantially the same as the first machine seat, is also located on the coupling nut and designed to accept a third O-ring. The function of the second and third O-rings are identical and will now be discussed.
The second and third O-rings are appropriately sized to form a seal across the annular region between the coupling nut and coupling ring. The coupling ring is machined to have a smooth inner surface at least over the distance the O-rings must travel past the female threads of the coupling ring. The smooth interior finish prevents damage to the O-rings during installation, permits smoother insertion into the coupling ring and facilitates water-tight seals.
The coupling ring is positioned for threadable engagement to the existing cable box. Each set of thread lengths, directions, and structure on both the coupling nut and the coupling ring are designed so that only the coupling ring is rotated to thread the 3 units together (coupling nut and cable, coupling ring, and cable box) and will tighten at the same time, preferably, to within xe2x85x9 of a turn at both the cable box/coupling ring interface and the coupling ring/coupling nut interface.
Once the cable box and coupling nut are both in position to be threadably engaged to the coupling ring, the coupling ring is rotated to simultaneously engage the coupling nut and cable box to the coupling ring.
The coupling ring is designed so that no special equipment is necessary and can be hand-tightened for proper attachment.
In the preferred embodiment, a smooth covering is snugly fitted over the coupling ring. The covering can be padded to or made of a deformable material which facilitates gripping by a human hand. The covering is used to discourage the use of tools which could be used to overtighten and damage the first O-ring seal.
The design of my invention encourages only hand-tightening since the seal performance of the O-rings across the annular region is independent of how tight the coupling ring is mated to the coupling nut. Therefore, a feature of my design is that specialized tools, or tools of any kind, are not required to properly tighten a communication cable to a cable box.